I have the following PowerShell script. It picks up the NetBIOS name of computers within a given IP address. I'm using a pipe so as to dump the results into a text file. The problem is that if an IP address is not available, a warning is printed.
This is the PowerShell script:
function Get-ComputerNameByIP {
param( $IPAddress = $null )
BEGIN {
$prefBackup = $WarningPreference
$WarningPreference = 'SilentlyContinue'
}
PROCESS {
if ($IPAddress -and $_) {
throw ‘Please use either pipeline or input parameter’
break
} elseif ($IPAddress) {
([System.Net.Dns]::GetHostbyAddress($IPAddress))
}
} else {
$IPAddress = Read-Host “Please supply the IP Address”
[System.Net.Dns]::GetHostbyAddress($IPAddress)
}
}
END {
$WarningPreference = $prefBackup
}
This is the error message I wish to ignore:
WARNING: The requested name is valid, but no data of the requested type was found
You want to suppress warnings, not errors. Warnings can be silenced completely by setting the $WarningPreference
variable to SilentlyContinue
:
PS C:\> Write-Warning 'foo'
WARNING: foo
PS C:\> $prefBackup = $WarningPreference
PS C:\> $WarningPreference = 'SilentlyContinue'
PS C:\> Write-Warning 'foo'
PS C:\> $WarningPreference = $prefBackup
PS C:\> Write-Warning 'foo'
WARNING: foo
The setting pertains to the current scope, so if you want to suppress all warnings for your function you'd simply set the preference at the beginning of your function:
function Get-ComputerNameByIP {
param( $IPAddress = $null )
BEGIN {
$WarningPreference = 'SilentlyContinue'
}
PROCESS {
if ($IPAddress -and $_) {
throw ‘Please use either pipeline or input parameter’
break
} elseif ($IPAddress) {
[System.Net.Dns]::GetHostbyAddress($IPAddress)
}
[System.Net.Dns]::GetHostbyAddress($_)
} else {
$IPAddress = Read-Host "Please supply the IP Address"
[System.Net.Dns]::GetHostbyAddress($IPAddress)
}
}
END {}
}
If you want warnings suppressed for specific statements only, a simpler way is to redirect the warning output stream to $null
:
[System.Net.Dns]::GetHostbyAddress($IPAddress) 3>$null
Warning stream redirection is only available in PowerShell v3 and newer, though.